Continuous Flow-stirred Tank Research Articles

Mathematical Kinetic Modelling and Representing Design Equation for a Packed Photoreactor with Immobilised TiO2-P25 Nanoparticles on Glass Beads in the Removal of C.I. Acid Orange 7

In this work, a design equation was presented for a batch-recirculated photoreactor composed of a packed bed reactor (PBR) with immobilised TiO2-P25 nanoparticle thin films on glass beads, and a continuous-flow stirred tank (CFST). The photoreactor was studied in order to remove C.I. Acid Orange 7 (AO7), a monoazo anionic dye from textile industry, by means of UV/TiO2 process. The effect of different operational parameters such as the initial concentration of contaminant, the volume of solution in CFST, the volumetric flow rate of liquid, and the power of light source in the removal efficiency were examined. A rate equation for the removal of AO7 is obtained by mathematical kinetic modelling. The results of reaction kinetic analysis indicate the conformity of removal kinetics with Langmuir-Hinshelwood model (kL-H = 0.74 mg L-1 min-1, Kads = 0.081 mg-1 L). The represented design equation obtained from mathematical kinetic modelling can properly predict the removal rate constant of the contaminant under different operational conditions (R2 = 0.963). Thus the calculated and experimental results are in good agreement with each other.

Changes in bacterial community during fermentative hydrogen and acid production from organic waste by thermophilic anaerobic microflora

Changes in fermentation pattern during the treatment of organic wastes containing solid materials by thermophilic anaerobic microflora were investigated with respect to product formation and bacterial community structure during hydrogen production. Anaerobic microflora enriched from sludge compost was cultivated using artificial garbage slurry in a continuous flow-stirred tank reactor. Product formation varied depending on pH and hydraulic retention time (HRT) applied. Community analysis by terminal restriction fragment length polymorphism and clone library analysis of polymerase chain reaction-amplified bacterial 16S rDNA indicated that difference in the fermentative product distribution could be caused by different populations of micro-organisms in the microflora. Hydrogen fermentation with acetate/butyrate formation was optimized at <1.0 d HRT at pH 5.0 and 6.0. Thermoanaerobacterium thermosaccharolyticum was the dominant hydrogen-producing micro-organism. Conversely, unidentified organisms became dominant after 4.0 d HRT at pH 7.0 and 8.0, where relatively high-solubilization efficiency of solid materials was observed with no production of hydrogen. This is the first report describing product formation in the fermentation of solid organic wastes by a mixed population of micro-organisms. Various fermentation patterns including hydrogen fermentation were characterized and evaluated from engineering and microbial aspects.

Polymer cross‐linking in post‐gel region for continuous and batch reactors

AbstractTetrafunctional chain coupling of polymers is an important process for introducing long‐chain branching to modify flow behavior and for forming cross‐linked networks. Reactor modeling for polymers branched beyond the gel point is a difficult problem because of the divergence of the moments of the MWD to infinity. A newly developed technique, numerical fractionation, based on the method of moments is applied to modeling chain coupling (cross‐linking) kinetics in continuous flow stirred tank (CFST) and batch reactors. The resulting model is applicable from 0 to 100% gelation and predicts the amount of sol fraction and its molecular weight and MWD as a function of operating conditions. This technique is easier to apply to reactor simulation than others for calculating properties of polymers in the post‐gel region. An examination of CFSR dynamics during reactor startup indicates a wide range of behavior depending on the critical residence time for gel formation. At residence times close to the critical, long times are needed to reach steady state, but at residence times much greater than the critical, the reactor can reach steady state in less than three turnovers. For both the batch and CFST reactors, polymer properties are determined by only two parameters: initial polymer MWD and reduced reaction time or reduced residence time. Consequently, at a given sol fraction, the molecular weight and MWD of the sol polymer are fixed. Narrowing the initial polymer MWD increases the amount of gel present at a given reaction time. Considerable differences are shown in the rate of the chain coupling reaction and properties of the sol phase between the two reactor types.

Carbon Isotope Effects on kcat for Formate Dehydrogenase Determined Using a Continuous-Flow Stirred-Tank Reactor

Carbon Isotope Effects on <i>k</i>_cat for Formate Dehydrogenase Determined Using a Continuous-Flow Stirred-Tank Reactor

Photo-induction of chemical oscillation in the Belousov—Zhabotinsky reaction under the flow condition

The photo-induction of chemical oscillation has been found in the Belousov—Zhabotinsky reaction in a continuous flow-stirred tank reactor. Photo-response of the system is characterized by taking the initial concentration of bromate ions and the incident light power as external control parameters. This characterization has lead us to conclude that the photo-irradiation in a certain range of control parameters can serve either to induce or to inhibit chemical oscillations depending on the light power.

Fish guts as chemical reactors: a model of the alimentary canals of marine herbivorous fishes

The alimentary canals of marine herbivorous fishes are variously composed of a few basic structures strung together in series. We model the structures where digestive processes occur as chemical reactors following the model of Penry and Jumars: the stomach as a batch or continuous-flow stirred-tank (CSTR), the intestine as a plug-flow reactor (PFR), and the hindgut caecum as a CSTR. Other structures, where food is mechanically processed-gill rakers, pharyngeal mills, and muscular stomachs-are classified as gates. The optimality criterion for the model is the digestion of the most nutrient in the least amount of time. With the model we are able to predict gut configuration as a function of nutrient concentration and hypothesize that the guts of herbivorous fishes always have a PFR component and may or may not have a CSTR component. The Penry-Jumars model appears to provide a consistent theoretical framework for four main types of digestive mechanisms in marine herbivorous fishes and offers specific testable hypotheses on the feeding ecology and digestive physiology of four representative species of fish as well as other, still unstudied, herbivorous fishes.

Diffusion from spheres in a continuous‐flow stirred tank

AbstractSolvent diffusion from spheres at constant mass‐transfer Fourier number, FoM, in a single continuous‐flow stirred tank (CFST) and in a series of CFSTs is simulated. A transfer efficiency is defined and transfer efficiency curves are constructed as a function of FoM and the residence time distribution of the spheres in the system. The fraction of solvent removed from the spheres in a series of CFSTs can be approximated using the transfer efficiency curves and knowledge of the operating conditions in each tank. The usefulness of the curves to predict solvent removal from polymer spheres under pilot‐plant conditions is examined.

Stirring effects and bistability in the iodate–arsenous acid reaction: Premixed vs segregated flows

Using a coalescence–dispersion model of the continuous flow-stirred tank reactor (CSTR), we study the effect of premixed vs nonpremixed reactant flows on chemical bistability. The region of bistability is smaller for segregated feed streams than for a fully premixed feed stream. The transition from flow branch to thermodynamic branch is particularly sensitive to the feed stream configuration.

Periodic Perturbations of Chemical Oscillators: Experiments

Periodic perturbations of chemical reactions have been the subject of many experimental studies in the past. Recall the early and exciting reports of submicrosecond relaxation times measured in ultrasonic adsorption, or in dielectric loss experiments in the 1950s and 1960s (1, 2). All these methods applied small periodic (or transient) pressure or electric field variations to chemical equilibria, in order to determine relaxation times and rate constants of elementary chemical steps. Because of its potential for increased yield, periodic operation of chemical reactions, particularly of polymerizations, has been studied extensively by chemical engineers (3-5) by the use of flow methods such as continuous flow-stirred tank reactor (CSTR). In the aforementioned systems the forcing perturbations were applied either to chemical equilibria or stable stationary states about which a small perturbation decays exponentially. In many a Gottingen tea hour iIi the 1960s a new question was raised: namely, how do chemical non­ sinusoidal limit cycles behave when they are periodically perturbed? Which type of response do they display? It had long been known then that a chemical oscillator that is damped should show normal resonance behavior. This was actually tested in a specifically designed experiment only recently (6). To sustain any oscillatory behavior the system has to be continuously replenished by reactants. By being open with respect to the influx of matter or energy (light, for example), the chemical oscillator is guaranteed to be far from chemical equilibrium in a defined nonequilibrium state characterized by a non-zero affinity. The 1970s saw a surge in the

Simulation of nonequimolecular polycondensation in continuous flow-stirred tank reactors

Conversion and molecular weight distribution are computed and compared for uncatalyzed and catalyzed nonequimolecular polycondensation in continuous flow-stirred tank reactors (CSTRs) using two different kinetic schemes proposed by Flory and Lin, respectively. The contrast between the two schemes is also remarkable as found in the batch reactors. The polydispersity indices in the CSTRs are substantially larger than those obtained in the batch reactors. Also, the molecular weight distribution splits into two curves for odd and even homologues regardless of the two different schemes. An extremely long rersidence time is needed to obtain the higher conversion accompanying a large polydispersity index as compared to the batch reactors. The polydispersity can be expressed in CSTR as x̄w/x̄n = 2 Σn2Nn(R+1−2P)/(1+R)2[A]0.